In recent years, in a dicing process for separating a silicon wafer (hereinafter called a wafer) forming a semiconductor integrated circuit and MEMS (Micro Electro Mechanical Systems) into respective semiconductor chips, consideration and research of a dicing process (laser dicing) using a laser beam are advanced. For example, a processing technique of the wafer using a laser is disclosed in JP-A-2002-192367. FIGS. 9A and 9B are explanatory views showing the dicing process using the laser beam. FIG. 9A is an explanatory view of a reforming area forming process using irradiation of the laser beam. FIG. 9B is an explanatory view of a divisional cutting process.
As shown in FIG. 9A, a laser head H for irradiating the laser beam L has a condenser lens CV for converging the laser beam L, and can converge the laser beam L at a predetermined focal distance. In the reforming area forming process, the laser head H is moved along a divisional cutting schedule line DL (in the direction of this side in FIGS. 9A and 9B) for divisionally cutting the wafer W in a laser beam irradiating condition set such that a convergent point P of the laser beam L is formed in a position of depth d from a substrate face of the wafer W. The laser beam L is irradiated from the substrate face of the wafer W. Thus, a reforming area K using multiphoton absorption is formed in a path of depth d in which the convergent point P of the laser beam L is scanned. When a foreign substance is attached onto the divisional cutting schedule line DL, the irradiation of the laser beam L is obstructed. Therefore, it is necessary to remove the foreign substance.
Here, the multiphoton absorption is that a substance absorbs plural photons of the same kind or different kinds. A phenomenon called optical damage is generated by this multiphoton absorption at the convergent point P of the semiconductor substrate W and its vicinity. Thus, thermal strain is induced, and a crack is generated in its portion. A layer constructed by gathering these cracks, i.e., the reforming area K is formed.
When the laser beam L is a pulse wave, intensity of the laser beam L is determined by peak power density (W/cm2) of the convergent point P. For example, the multiphoton absorption is generated in a condition in which peak power density is 1×108 (W/cm2) or more and pulse width is 1 μs or less. For example, a laser beam using a YAG (Yttrium Aluminum Garnet) laser is used as the laser beam L. For example, the wavelength of this laser beam L is a wavelength of 1064 nm in an infrared light area.
Subsequently, as shown in FIG. 9B, stress is loaded in an in-plane direction (direction shown by arrows F2 and F3 in this figure) of the semiconductor substrate W. Thus, a crack C is developed in the substrate thickness direction with the reforming area K as a starting point, and the semiconductor substrate W is divisionally cut along the divisional cutting schedule line DL. At a divisional cutting time, one portion of the semiconductor substrate W is chipped, and dust is generated. When this dust is attached to the substrate face, there is a fear that this dust has a bad influence on a product. Therefore, it is necessary to remove this dust.
As a method for removing an attachment substance such as dust, a foreign substance, etc. mentioned above, a technique for removing the attachment substance by suction and a technique for blowing-off the attachment substance by air cleaning are disclosed in, for example, JP-A-2003-10986 and JP-A-2003-10992.
However, in the removal using suction, there is a problem of a fear that the attachment substance is moved in a wide range along the semiconductor substrate at a sucking time, and has a bad influence such as damage of a product, etc. There is also a problem that the attachment substance can be removed in only a narrow area near a sucking portion, and removing efficiency is bad. Further, in the air cleaning, there is a problem of a fear that the attachment substance is moved in a wide range along the semiconductor substrate, and has a bad influence such as damage of a product, etc.
Further, a manufacturing device of a semiconductor chip is formerly used in manufacture of the semiconductor chip. In this manufacturing device, with respect to the semiconductor substrate of a state diced on a divisional scheduled line and stuck to a sheet, this sheet is extended and enlarged, and the semiconductor substrate is divided into semiconductor chips by loading stress in a planar direction of the semiconductor substrate. FIGS. 16A and 16B show one example of a former manufacturing device of the semiconductor chip. FIG. 16A is an explanatory view of a state in which the semiconductor substrate is adhered to the sheet and an outer circumferential portion of the sheet is held in a frame. FIG. 16B is an explanatory view of a process for dividing the semiconductor substrate into semiconductor chips by a pressing device.
As shown in FIG. 16A, the substrate face of a rear face of the semiconductor substrate, i.e., the semiconductor wafer W constructed by a semiconductor of silicon, etc. is adhered to the sheet S manufactured by resin and having a drawing property in a state in which laser dicing, etc. are performed. An outer circumferential portion of the sheet S is held by a frame F of an annular shape.
As shown in FIG. 16B, the semiconductor substrate W is pressed so as to be pushed up from the rear side of the sheet S by using a pressing device PD arranged below the semiconductor substrate W and moved in the vertical direction by an unillustrated moving means. Thus, the sheet S is extended in the planar direction (the directions of arrows F11 and F12 in FIG. 16B). Thus, stress is loaded to the semiconductor substrate W adhered to the sheet S in the planar direction. Therefore, the semiconductor substrate W is divided into plural semiconductor chips C. The above device is disclosed in JP-A-2003-334675.
However, in the former manufacturing device of the semiconductor chip, the sheet S is extended in a state in which the outer circumference of the sheet S is held. Therefore, the extension of the sheet S tends to become large toward its outer circumferential portion, and the extension of the sheet S tends to become small in its central portion. Namely, the semiconductor substrate W is properly divided in the vicinity of the outer circumference, but no semiconductor substrate W is easily divided in the vicinity of the center. Therefore, a problem exists in that yield of the semiconductor chip C is reduced.
Further, it is preferable to uniformly extend the sheet S so as to improve yield for obtaining the semiconductor chip C by divisionally cutting the semiconductor substrate W. However, in the former divisional cutting device of the semiconductor substrate, the sheet S is extended in a holding state of the outer circumference of the sheet S. Therefore, the extension of the sheet S tends to become large toward its outer circumferential portion, and tends to become small in its central portion. Namely, the semiconductor substrate W is properly divisionally cut near the outer circumference, but is not easily divisionally cut near the center. Therefore, a problem exists in that yield of the semiconductor chip C is reduced.